Missfire at 7k under load

[Spike16]

Ok today was the first time out on my road nc30 for a long time (almost 4 months) as iv been at uni then decided to put her away for winter, and she's not really been started over that time

I went out and their is a massive missfire at about 7k revs where it feels like it goes to about 2 cylinders, sound like an old bonnie!, not cool, but then if you push through it revs up but is still missing, like its on 3 cylidners now.


what could this be? my recon is shitted up carbs and old fuel does anyone agree? or is their anything else that I could be overlooking

[ibby4585]

Spike, i had this on my 89' NC last week, I sprayed shit loads of carbs spray in the carbs and changed the plugs, the plugs were really fouled up with oil and petrol!! Its much better now, and is clean right the way through the rev range, reckon it would be even better if i took the carbs off and gave them a clean. Mine wasnt started for 3 months so it could be the same with yours!!

Kris

[eamer1989]

See thats weird peoples plugs mucking around and old fuel and carbs just become crap due to left over fuel

Started my bike up after 8 months sitting and it fired on the dot with no problem was running little rubbish threw rev range but after 5mins of riding it was cleared and ran perfect. anyhow all bikes behave diffrently i suppose

[Sligeach]

my bike generally sits for about 2 months at any one time, its in a heated garage (which i think yours is too). when i first start it up it sounds shitty but after a clearout and a bit of fresh juice it is fine.
just go for a ride, roads are dry around me!!

[Cammo]

Did you drain the carbs before laying it up Spike?

[Spike16]

no didnt drain it as I didnt think it would be so long before I rode it again, plan was to take it to uni with me. its in a garage but its not heated and its wierd cos iv had over a year of faultless riding from it and now its gone all funny ah well il rebuild the carbs and hopefully that will sort it out

[eamer1989]

mines under a carport with a cover over it, never drained carbs dunno just something about my road nc30 never wants to give up lol, apart from i have a heating issue but i will have a look at that as soon as i finish race build

[Neosophist]

no didnt drain it as I didnt think it would be so long before I rode it again, plan was to take it to uni with me. its in a garage but its not heated and its wierd cos iv had over a year of faultless riding from it and now its gone all funny ah well il rebuild the carbs and hopefully that will sort it out

Your carbs are gonna be gummed up :) The slow jets are fine and petrol goes manky quickly.

If your not draining it get someone to run it once every fortnight, let it idle, then warm it up (rev it up through the rev range) (sit the bike up level whilst doing this to get maximum oil to the pump) and let the fan kick in at least TWICE.. doing this not only runs petrol through the carbs and engine, but circulates the oil and burns off most of the condensation that'll form in the oil / downpipes etc :)

It'll also run your petrol out forcing you to buy new petrol, which if you do twice a month means you never have really stale fuel in the tank which'll also cause hard starting.